I like Amanda Marcotte’s explication at Slate:
Now that the shock of losing has settled in, the conservative media has moved on to the important task of castigating the various demographics that broke for Obama, a reaction that can in no way be one of the reasons said demographics dislike Republicans. Since Obama won basically everyone but nonurban white men and their wives, there are a lot of different groups to hate on, but a clear front-runner in the Blame Game has emerged: single women, who gave 68 percent of their vote to Obama, compared to 53 percent of married women who voted for Romney.
There are many reasons for this divergence, including age, income, and racial differences between the single and married women, but right-wing media looks to be settling on a favorite explanation: Loose gals vote Obama. Unlike, say, Sean Hannity’s now evolving position on immigration, clearly morphing in order to somehow get his guys a few Latino votes, this impulse to label single women as sluts is certainly no one’s idea of voter outreach. But it does serve the dual purpose of demonizing Obama voters and reminding Fox News and rightwing talk radio audiences of their favorite porn narratives…
Because some things must be said (sung):